Stripper solutions effective for back-end-of-line operations

ABSTRACT

Back end of line (BEOL) stripping solutions which can be used in a stripping process that replaces etching resist ashing process are provided. The stripping solutions are useful for fabricating circuits and/or forming electrodes on semiconductor devices for semiconductor integrated circuits with good efficiency and with low and acceptable metal etch rates. Methods for their use are similarly provided. The preferred stripping agents contain a polar aprotic solvent, water, an amine and a quaternary hydroxide that is not tetramethylammonium hydroxide. Further provided are integrated circuit devices and electronic interconnect structures prepared according to these methods.

This application is a continuation of U.S. patent application Ser. No.12/490,654 filed Jun. 24, 2009 which claims the benefit of U.S.Provisional Application No. 61/075,195, filed Jun. 24, 2008, which ishereby incorporated by reference.

FIELD OF THE INVENTION

The present disclosure relates to a back-end-of-line (BEOL) strippingagent for use in fabricating circuits or forming electrodes onsemiconductor devices for semiconductor integrated circuits or liquidcrystal displays, semiconductor devices made with the new BEOL strippingagent, and further to a process of producing semiconductor devices usingthe BEOL stripping agent and for producing the BEOL stripping agent.

BACKGROUND

The technology of fabricating semiconductor integrated circuits hasadvanced with regard to the number of transistors, capacitors and otherelectronic devices which can be fabricated on a single integratedcircuit chip. This increasing level of integration has resulted in largepart from a reduction in the minimum feature sizes of the integratedcircuits and an increase in the number of layers which make up theintegrated circuit. Today's design features, generally referred to as“sub-micron” have dropped below 0.25 microns. The manufacture ofintegrated circuit components having this reduced size and the need toreduce production steps has placed new demands on all aspects of theirproduction including the removal of resists and related materials withchemical stripper solutions.

Semiconductor devices for semiconductor integrated circuits or liquidcrystal displays are commonly produced by a process including the stepsof coating a substrate with one or more layers of polymeric resistmaterials to provide a resist film; patterning the photosensitive resistfilm by exposure to light and subsequent development; etching exposedportions of the substrate using the patterned resist film as a mask toform minute circuits; and removing the resist film from the inorganicsubstrate. Alternatively, after forming minute circuits, the post etchresidues can be ashed and the remaining resist residues removed from thesubstrate with a post etch residue remover. This portion of circuitfabrication is referred to as the back-end-of-line (BEOL) fabrication.What is needed is a BEOL stripper solution which can remove remainingphotoresists and post etch residues in a single step.

A superior BEOL stripper solution should: (a) quickly and cleanly removeresist residues, etch residues and related materials at moderate to lowtemperatures without requiring a final ashing or post etch removal step,(b) have an acceptable effect on the all exposed components,particularly the underlying low or ultra low-κ dielectric and metals,(c) have a substantial capacity to dissolve and/or suspend resist and/orpost etch residue to forestall precipitation and/or re-deposition ofsolid onto the wafer necessitating the early disposal of the strippersolution, (d) be safe to use in a manufacturing environment, (e) have anacceptable shelf-life and (f) be backward compatible with lowertechnology nodes. A superior BEOL stripper solution should also quicklyremove resist residues in a rework process without substrate damage.Finally, superior stripper solutions should exhibit minimal toxicity.This present disclosure addresses and resolves these needs.

SUMMARY

A general object of the present invention is to provide a compositionfor removing a photoresist, residue, and related materials from aback-end-of-line (BEOL) operation, a method for utilizing thecomposition in the manufacture of a semiconductor structure, and asemiconductor structure manufactured utilizing the composition.Preferred embodiments of the composition can be utilized without etchingor otherwise damaging metals and/or dielectric material contained in oron the semiconductor structure. As used herein, the term resist refersto a photoresist or resist material, a post etch residue, or acombination thereof.

One object of the present disclosure is a BEOL stripper compositionwhich includes a polar aprotic solvent, water, an amine and a quaternaryhydroxide. Suitable quaternary hydroxides are represented by formula I,provided below:

where Z is N or P and R¹, R², R³, and R⁴ are alkyl groups, aryl groups,or a combination thereof having collectively at least 5 carbons. Thepreferred BEOL stripper solutions contain substantially notetramethylammonium hydroxide. For preferred BEOL stripper solutions,the amine is a hydroxy-substituted alkylamine and/or an alkyl ether of ahydroxy-substituted alkylamine. A particularly preferredhydroxy-substituted alkylamine is monoethanolamine and a preferred amineether is the methyl ether of a hydroxy-substituted alkylamine. For thepreferred BEOL stripper solutions, the polar aprotic solvent is dimethylsulfoxide (DMSO). Although the concentrations of DMSO can range fromabout 20% to about 95%, in the preferred BEOL solutions, the aproticsolvent concentration generally ranges from about 40 to about 90 weightper cent, more preferably from about 55 to about 90 weight per cent.Water content for the preferred solutions generally ranges from about 2to about 15 weight per cent. However, the optimum amount of water canvary depending on the selection of the other components and theirproportions. Although the BEOL stripper solutions described herein havebeen optimized for BEOL applications, these stripper solutions can beused to remove photoresists, etch residues, and the like in a variety ofother standard applications including, but not limited to (i) high doseimplant resist removal, (ii) post etch residue in gate formation, (iii)post etch residue in floating gate formation, and (iv) re-workapplications.

Another object of the present disclosure is to provide a method forremoving a resist film from a substrate in a BEOL process. The methodincludes the steps of providing a substrate having a component selectedfrom the group consisting of photoresists, planarizing materials,photoresist residues, and the like thereon, and contacting the substratewith a composition including the BEOL stripper solution to effectremoval of the photoresist and related materials. Photoresists,planarizing materials, photoresist residues, and the like arecollectively referred to herein as “resists.” Preferred BEOL strippersolutions used in the contacting step include those described above. Thestep of contacting can involve immersion of a substrate in a strippersolution or by spraying the stripper solution onto the substrate using aspray tool, with or without other cleaning aids such as for examplemegasonics. Further steps following contacting can involve theadditional steps of removing the substrate from contact with thestripper solution and/or rinsing the substrate with an appropriatesolvent. During the contacting step, the stripper solution is preferablymaintained at a temperature of at least about 40° C. and more preferablyat a temperature ranging from about 50° C. to about 75° C.

An important substrate property is a low-κ permittivity value. Thisvalue can change, typically increase, following contact with a strippersolution. This change in the low-κ permittivity value (Δ κ) can beminimized by removing volatiles from the substrate following contactwith the stripper solution and a rinsing step. Volatiles can be removedfrom a treated substrate by heating the substrate, subjecting thesubstrate to a reduced pressure, or a combination thereof. Removal canoccur as a result of a treatment specifically designed to removevolatiles or occur coincidentally during subsequent processing stepsthat involve heating and/or vacuum treatment. With current technology,it is desirable that the removal of a resist from a substrate result ina change in the low-κ permittivity value of ≦0.1

Another object of the present disclosure is to provide an electronicinterconnect structure prepared in part by removing resists, resistresidues, and the like from a substrate having metal componentsaccording to the method described above to produce an interconnectstructure with a reduced number of etching processes and providingreduced damage to the structure. FIG. 4 illustrates a typical electronicinterconnect structure having trenches 1 and 2 interconnected throughvia 3 within two dielectric layers 5 and 6 separated by a barrier layer4, Trenches 1 and 2 and via 3 are typically filled with a metal such ascopper, aluminum, or alloys containing these metals. Corrosion and/oretching of these metals are typically reduced when the preferred BEOLstripper solutions are utilized in the preparation of the electronicinterconnects.

Another object of the present disclosure is to provide an integratedcircuit device obtainable in part by processing wafers containing metalcomponents to remove resist residues according to the method describedabove with reduced metal etching. FIG. 5 illustrates a typicalintegrated circuit device having a plurality of computer chipsillustrated by I interconnected through chip routers illustrated by 2.

A still further object of the present disclosure is to provide a methodfor preparing a BEOL stripper solution by providing a container;providing the components of a stripper solution; and adding thecomponents to the container to provide contents within the container.Providing components can include providing individual components, acomposition containing various components, or combinations thereof.Further, adding components of a stripper solution can involve addingindividual components, premixed components, and/or a preformed strippersolution containing provided components in substantially any order.Preferred components include a polar aprotic organic solvent, water, anamine, and a quaternary hydroxide, where the quaternary hydroxide hasthe formula:

where Z is N or P and R¹, R², R³, and R⁴ are alkyl groups, aryl groups,or a combination thereof having collectively at least 5 carbons. Acontainer can include substantially any vessel capable of holding astripper solution and includes a typical container used for shipping ortransporting a liquid product, equipment used to contain strippersolutions for use processing substrates to remove photoresists and/oretch residues. As used herein a vessel includes equipment used to holdand/or transport a stripper solution during the processing of substratesand includes, but is not limited to holding and transfer vesselsincluding any pipe system used to transport a stripper solution.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A provides an SEM (top view) of a via array after an unsuccessfulcleaning procedure that would be considered not clean (NC).

FIG. 1B provides an SEM (top view) of a single via after an unsuccessfulcleaning procedure that would be considered not clean (NC).

FIG. 2A provides an SEM (top view) of a via array after a successfulcleaning procedure that would be considered clean (C).

FIG. 2B provides an SEM (cross section) of a via array after asuccessful cleaning procedure that would be considered clean (C).

FIG. 2C provides an SEM (top view) of a single via after an successfulcleaning procedure that would be considered clean (C).

FIG. 3A provides an SEM (top view) of a via array after a successfulcleaning procedure that resulted in extensive etch damage to the low kdielectric.

FIG. 3B provides an SEM (top view) of a via after a successful cleaningprocedure that resulted in extensive etch damage to the low Kdielectric.

FIG. 4 illustrates an electronic interconnect structure.

FIG. 5 illustrates an electronic device containing a plurality ofelectronic interconnect structures.

FIG. 6 illustrates a typical photoresist or resist stack.

DESCRIPTION

For the purposes of promoting an understanding of the presentdisclosure, references will now be made to the embodiments illustratedand specific language will be used to describe the same. It willnevertheless be understood that no limitation of the scope of what isclaimed is thereby intended, such alterations and further modificationsand such further applications of the principles thereof as illustratedtherein being contemplated as would normally occur to one skilled in theart to which the disclosure relates.

As used herein, back-end-of line or BEOL, refers to the part ofintegrated circuit fabrication where transistors, resistors, and thelike are interconnected with the wiring. The BEOL portion of fabricationtypically begins with patterning for the first metal contact or withdeposition of the first layer of metal onto the wafer.

The compositions according to this present disclosure include a BEOLstripper solution containing a polar aprotic solvent, water, and anamine and a quaternary hydroxide. Preferred stripper solutions comprisedimethyl sulfoxide, water, an amine and a quaternary hydroxiderepresented by the following formula:

where Z is N or P and R¹, R², R³, and R⁴ are alkyl groups, aryl groups,or a combination thereof having collectively at least 5 carbons. TheBEOL stripper solutions can also contain an alkanolamine or the alkylether of an alkanolamine. Preferred quaternary hydroxides includetetrabutylammonium hydroxide and tetrabutylphosphonium hydroxide.Particularly preferred BEOL stripper solutions are also substantiallyfree of tetramethylammonium hydroxide (“TMAH”). A stripper solution thatcontains less than about 0.5% TMAH is considered to be substantiallyfree of TMAH.

The compositions typically contain about 20% to about 95%, and morepreferably from about 40% to about 90% of a polar aprotic solvent suchas, for example, DMSO and from about 2% to about 10% of the quaternaryhydroxide. Preferred quaternary substituents include (C₁-C₈) alkyl,benzyl, aryl and combinations thereof provided that the number ofcarbons included in the four substituents is at least 5. The strippingformulations can also contain an optional surfactant, typically atlevels in the range of about 0.01% to about 3% or more preferably in therange of from about 0.01 to about 2%. Suitable levels of the requiredalkanolamine can range from about 2% to about 60% of the composition.The preferred compositions tested so far also include from about 2% toabout 10% water. All %'s provided herein are weight per cents.

Preferred alkanolamines have at least two carbon atoms and have theamino and hydroxyl substituents on different carbon atoms. Suitablealkanolamines include, but are not limited to, ethanolamine,N-methylethanolamine, N-ethylethanolamine, N-propylethanolamine,N-butylethanolamine, diethanolamine, triethanolamine,N-methyldiethanolamine, N-ethyldiethanolamine, isopropanolamine,diisopropanolamine, triisopropanolamine, N-methylisopropanolamine,N-ethylisopropanolamine, N-propylisopropanolamine, 2-aminopropane-1-ol,N-methyl-2-aminopropane-1-ol, N-ethyl-2-aminopropane-1-ol,1-aminopropane-3-ol, N-methyl-1-aminopropane-3-ol,N-ethyl-1-aminopropane-3-ol, 1-aminobutane-2-ol,N-methyl-1-aminobutane-2-ol, N-ethyl-1-aminobutane-2-ol,2-aminobutane-1-ol, N-methyl-2-aminobutane-1-ol,N-ethyl-2-aminobutane-1-o1, 3-aminobutane-1-ol,N-methyl-3-aminobutane-1-ol, N-ethyl-3-aminobutane-1-ol,1-aminobutane-4-ol, N-methyl-1-aminobutane-4-ol,N-ethyl-1-aminobutane-4-ol, 1-amino-2-methylpropane-2-ol,2-amino-2-methylpropane-1-ol, 1-aminopentane-4-ol,2-amino-4-methylpentane-l-ol, 2-aminohexane-1-ol, 3-aminoheptane-4-ol,1-aminooctane-2-ol, 5-aminooctane-4-ol, 1-aminopropane-2,3-diol,2-aminopropane-1,3-diol, tris(oxymethyl)aminomethane,1,2-diaminopropane-3-ol, 1,3-diaminopropane-2-ol, and2-(2-aminoethoxy)ethanol. Ethers of the preferred alkanolamines cansimilarly be utilized.

Although not required, formulations of the stripper solutions canadditionally contain a corrosion inhibitor to further minimize any metalcorrosion during contact with the stripper solution. Suitable corrosioninhibitors include, but are not limited to, Cu(I) and Cu(II) salts,aromatic hydroxyl compounds such as catechol; alkylcatechols such asmethylcatechol, ethylcatechol and t-butylcatechol, resorcinols, phenolsand pyrogallol; aromatic triazoles such as benzotriazole;alkylbenzotriazoles; carboxylic acids such as formic acid, acetic acid,propionic acid, butyric acid, isobutyric acid, oxalic acid, malonicacid, succinic acid, glutaric acid, maleic acid, fumaric acid, benzoicacid, phtahlic acid, 1,2,3-benzenetricarboxylic acid, glycolic acid,lactic acid, malic acid, citric acid, acetic anhydride, phthalicanhydride, maleic anhydride, succinic anhydride, salicylic acid, gallicacid, and gallic acid esters such as methyl gallate and propyl gallate;organic salts of carboxyl containing organic containing compoundsdescribed above, ethyl silicate, basic substances such as ethanolamine,trimethylamine, diethylamine and pyridines, such as 2-aminopyridine, andthe like, and chelate compounds such as phosphoric acid-based chelatecompounds including 1,2-propanediaminetetramethylene phosphonic acid andhydroxyethane phosphonic acid, carboxylic acid-based chelate compoundssuch as ethylenediaminetetraacetic acid and its sodium and ammoniumsalts, dihydroxyethylglycine and nitrilotriacetic acid, amine-basedchelate compounds such as bipyridine, tetraphenylporphyrin andphenanthroline, and oxime-based chelate compounds such asdimethylglyoxime and diphenylglyoxime. A single corrosion inhibitor maybe used or a combination of corrosion inhibitors may be used.

Examples of suitable corrosion inhibitors useful in the BEOL strippersolutions are described in U.S. patent application Ser. No. 11/928,754,filed on Oct. 30, 2007, and in U.S. patent application Ser. No.11/928,728, filed on Oct. 30, 2007. Corrosion inhibitors have typicallyproven useful at levels ranging from about 1 ppm to about 10%.

Preferred stripper solutions can also be formulated to minimize orprevent damage to the low or ultra low-κ dielectric layers present in awafer. One approach involves the addition of a dielectric damageinhibitor such as glycerine. Suitable levels of glycerin or otherinhibitor are currently believed to be in the order of about 0.25 to 1%.A second approach involves replacement of a low molecular weightalkanolamine with a higher molecular weight alkanolamine. Reduced damageto the dielectric layer has been achieved by replacing, on a gram forgram basis, monoethanolamine with aminoethylethanolamine.

Preferred optional surfactants have included fluorosurfactants. Oneexample of a preferred fluorosurfactant is DuPont FSO (fluorinatedtelomere B monoether with polyethylene glycol (50%), ethylene glycol(25%), 1,4-dioxane (<0.1%), water 25%). Preferred temperatures of atleast 40° C. are preferred for contacting the substrate whereas for amajority of applications, temperatures of from about 50° C. to about 75°C. are more preferred, For particular applications where the substrateis either sensitive or longer removal times are required, lowercontacting temperatures are appropriate. For example, when reworkingsubstrates, it may be appropriate to maintain the stripper solution at alower temperature for a longer time to remove the photoresist and avoiddamaging to the substrate. If longer contact times are required forcomplete resist removal, placing a blanket of dry nitrogen over thestripper solution can reduce water uptake from the atmosphere andmaintain the dry stripper solution's improved performance.

When immersing a substrate, agitation of the composition additionallyfacilitates photoresist removal. Agitation can be effected by mechanicalstirring, circulating, by bubbling an inert gas through the composition,or any combination thereof. Upon removal of the desired amount of resistfilm, the substrate is removed from contact with the stripper solutionand rinsed with water, an alcohol, or a mixture thereof. DI water is apreferred form of water and isopropanol is a preferred alcohol. Forsubstrates having components subject to oxidation, rinsing can be doneunder an inert atmosphere. The preferred stripper solutions according tothe present disclosure have improved loading capacities for photoresistmaterials compared to current commercial products and are able toprocess a larger number of substrates with a given volume of strippersolution. As used herein, loading capacity refers to the ability of astripper solution to dissolve, suspend, or otherwise avoid precipitationand/or re-deposition of a solid onto a wafer being cleaned.

In addition to immersion techniques, wafers can also be contacted with astripper solution utilizing a spray device with the stripper solutionmaintained at the desired temperature. The spraying can optionally becarried out using additional cleaning aids including ultrasonics and/orunder an inert atmosphere or optionally in the presence of an active gassuch as, for example, oxygen or ozone. The wafer can be removedperiodically and inspected to determine when sufficient cleaning hasoccurred. The clean wafer can be rinsed with isopropanol and dried. Thismethod can be used to remove multiple layers of resist and as a BEOLcleaning step.

Additionally, wafers containing resist stacks having one or multiplelayers of positive and/or negative resists can also be processed bythese methods. Typical resist stacks can include, but are not limitedto, one or multiple layers of resist which can include, for example, aplanarizing layer, a bottom antireflection coating layer, a hard mask,and/or a photoresist. FIG. 6 illustrates a typical generic via firstresist stack that includes: (a) an ultra low-κ dielectric 10, (b) aplanarizing material 12 within and above the vias 16 and the dielectric10, (c) a hard mask 13 in contact with the planarizing material 12, (d)a bottom antireflection coating 14 in contact with the hard mask 13, and(e) a photoresist 18. FIG. 6 is provided to illustrate the relationshipbetween layers in one type of typical stack layer and is not meant tolimit the utility of the stripper solutions disclosed. One skilled inthe art will recognize that other combinations of layers can be utilizeddepending on the process being utilized and the materials selected andthat the solutions disclosed can similarly remove these other stacklayer combinations.

FIG. 1A provides an SEM (top view) of a via array illustrating a “notclean” (NC) result. FIG. 1B provides an SEM (top view) of a single viaillustrating a “not clean” (NC) result. FIG. 2A provides an SEM (topview) of a via array illustrating a “clean” (C) result. FIG. 2B providesan SEM of a via array illustrating a “clean” (C) result. FIG. 2Cprovides an SEM (top view) of a single via illustrating a “clean” (C)result. FIG. 3A provides an SEM (top view) of a via array illustrating awafer having extensive etching of the low-κ dielectric. FIG. 3B providesan SEM (top view) of a single via illustrating extensive etching of thelow-κ dielectric.

METHODOLOGIES USED IN EXAMPLES

The components for the formulation tested in the following Examples werecombined with stirring at room temperature to give 100 g of ahomogeneous stripper solution. The solution was heated to 65° C. withslow agitation. Patterned test wafers with via and trench patternsformed in ultra low-κ black diamond II were obtained. The test wafersstill had their photoresist stack present, and had not been cleaned orprocessed further after pattern transfer into the ultra low-κ blackdiamond II. The patterned test wafers were cleaved into ˜4 cm×3 cmpieces and mounted into a small scale wafer holder.

Unless otherwise noted in a Table, each stripper solution was heated to65° C. and a wafer piece immersed. The timer was started as soon as theywere fully immersed. Immersion was maintained 1, 3, 5, or 10 minutes,after which the wafer was rinsed with isopropanol and dried. Sampleswere evaluated as clean (C) if substantially all materials had beenremoved and not clean (NC) if substantially all materials had not beenremoved. FIGS. 1A, 1B, 2A, 2B, 2C, 3A, and 3B illustrate what is meantby C and NC. As can be determined by the FIGS. not clean (NC) did notmean that no cleaning at all had occurred. The methods can similarly becarried out with a spray tool.

For imaging, the sample was cleaved into 2 cm×3 cm pieces and thesurface was gently flushed to remove dust and particles. Samples werepropped in sputter chamber at an approximately 30° angle with cleavededge facing upward. The chamber was pumped down to 20 mTorr before Argas was bled in to a pressure of 50 mTorr. The power supply was turnedon and adjusted to 20 mA. Samples were sputtered for 100 s [Pd target,4″ diameter, ⅛^(th) inch thick from Ted Pella] to deposit approximately0.8 nm of Pd metal on the sample surface. Scanning electron microscopy(SEM) images were obtained on either an FEI Sirion FE-SEM with 1-3 nmresolution, or a Hitachi S-4800 UHR FE-SEM with 1-1.4 nm resolution.

Example 1 Resist Removal Formulations

Test samples obtained and prepared as described above were immersed intest samples of stripper solutions for 1, 2, 3, and 4 minute intervalsand evaluated for cleaning as described above. The results for severaldifferent stripper formulations are provided in Table I below. As shownin Table 1, the inclusion of an alkanolamine or its ether can improvecleaning performance, and the selection of the specific alkanolamine andits concentration can further impact the stripper solution's cleaningperformance.

TABLE 1 Cleaning Result (min.) at 65° C. Example Formulation 1 2 3 4 1-a87 g DMSO 5.5 g tetrabutylammonium hydroxide NC C C C 4.5 g H₂O 1-b 87 gDMSO 5.5 g tetrabutylammonium hydroxide C C C C 4.5 g H₂O 3 gmonoethanolamine 1-c 87 g DMSO 5.5 g tetrabutylammonium hydroxide NC C CC 4.5 g H₂O 3 g tertiary butylaminoethanol 1-d 87 g DMSO 5.5 gtetrabutylammonium hydroxide NC NC C C 4.5 g H₂O 3 g2-amino-2-methyl-l-propanol 1-e 87 g DMSO 5.5 g tetrabutylammoniumhydroxide NC C C C 4.5 g H₂O 3 g N,N-dimethylamino-l-propanol 1-f 65 gDMSO 5.5 g tetrabutylammonium hydroxide NC NC NC NC 4.5 g H₂O 25 gaminoethylethanolamine 1-g 84 g DMSO 5.5 g tetrabutylammonium hydroxideC C C C 4.5 g H₂O 6 g monoethanolamine 1-h 83 g DMSO 3 gdiethyldimethylammonium hydroxide C C C C 11 g H₂O 3 g monoethanolamine1-i 81 g DMSO 3 g methyltriethylammonium hydroxide C C C C 13 g H₂O 3 gmonoethanolamine 1-j 86 g DMSO 5.5 g tetrabutylammonium hydroxide C C CC 4.5 g H₂O 4 g 1-amino-2-methoxyethane 1-k 93.5 g DMSO 3 gtetrabutylammonium hydroxide NC C C C 2 g H₂O 1.5 g monoethanolamine 1-l87 g DMSO 4 g tetrapropylammonium hydroxide NC C C C 6 g H₂O 3 gmonoethanolamine C = clean and NC = not clean

Example 2 The Negative Effect of Tetramethylammonium Hydroxide onCleaning

As noted in Table 2, the addition of varying amounts oftetramethylammonium hydroxide to a stripper solution interfered with thecleaning process and in some instances caused etching of the low-κdielectric.

TABLE 2 Cleaning Result (min. ) at 65° C. Example Formulation 1 2 3 42-a 87 g DMSO C C C C 5.5 g tetrabutylammonium hydroxide 4.5 g H₂O 3 gmonoethanolamine 2-b 89 g DMSO NC NC NC NC 3 g tetrabutylammoniumhydroxide 1 g tetramethylammonium hydroxide 4 g H₂O 3 g monoethanolamine2-c 90 g DMSO NC NC NC NC* 3.5 g tetrabutylammonium hydroxide 0.5 gtetramethylammonium hydroxide 3 g H₂O 3 g tertiary monoethanolamine 2-d87.5 g DMSO NC NC NC NC* 5 g tetrabutylammonium hydroxide 0.2 gtetramethylammonium hydroxide 4.3 g H₂O 3 g monoethanolamine 2-e 70 gDMSO NC NC NC NC 5 g tetrabutylammonium hydroxide 5 g H₂O 20 gmonoethanolamine C = clean; NC = not clean, *= badly etched low-κdielectric

Example 3 The Effect of Water Concentration

The data provided in Table 3 illustrates that: (a) a stripper solutionwith no water performed poorly, (b) the addition of some water improvedthe cleaning performance of the solution, and (c) the addition of toomuch water caused etching of the low-κ dielectric with longer contacttimes.

TABLE 3 Cleaning Result (min.) at 65° C. Example Formulation 1 2 3 4 3-a42 g DMSO NC NC NC NC 5.5 g tetrabutylammonium hydroxide 49.5 gpropylene glycol 3 g monoethanolamine 3-b 87 g DMSO NC C C C 5.5 gtetrabutylammonium hydroxide 2.2 g H₂O 3 g monoethanolamine 3-c 87 gDMSO C C C C 5.5 g tetrabutylammonium hydroxide 4.5 g H₂O 3 gmonoethanolamine 3-d 87 g DMSO C C* C* C* 5.5 g tetrabutylammoniumhydroxide 7.5 g H₂O 3 g monoethanolamine C = clean; NC = not clean, *=badly etched low-κ dielectric

Example 4 Temperature Effect on Cleaning

Information regarding cleaning performance as a function of temperatureis provided in. Table 4, below.

TABLE 4 Cleaning Result at one minute Example Formulation 55° C. 60° C.65° C. 70° C. 4 87 g DMSO NC NC C C 5.5 g tetrabutylammonium hydroxide4.5 g H₂O 3 g monoethanolamine C = clean and NC = not clean

Example 5 A Stripper Solution containing a Quaternary PhosphoniumHydroxide

A stripper solution containing tetrabutylphosphonium hydroxide cleanedeffectively and showed little effect on the low-κ dielectric.Additionally, other quaternary phosphonium hydroxides can be utilized tooptimize cleaning performance.

TABLE 5 Cleaning Result (min.) at 65° C. Example Formulation 1 2 3 4 5-a81 g DMSO C C C C 7 g tetrabutylphosphonium hydroxide 9 g H₂O 3 gmonoethanolamine 5-b 81 g DMSO NC NC C C 7 g tetrabutylphosphoniumhydroxide 9 g H₂O 3 g amino ethylethanolamine 5-c 80.5 g DMSO C C C C 7g tetrabutylphosphonium hydroxide 9 g H₂O 3 g monoethanolamine 0.5 gglycerine C = clean and NC = not clean

Example 6 A Second Polar Aprotic Solvent

As illustrated in Table 6, the stripper solutions can contain a secondpolar aprotic solvent and maintain desired cleaning levels.

TABLE 6 Cleaning Result (min.) at 65° C. Example Formulation 1 2 3 4 2-a87 g DMSO C C C C 5.5 g tetrabutylammonium hydroxide 4.5 g H₂O 3 gmonoethanolamine 6-a 86.5 g DMSO C C C C 0.5 g 1-formylpiperidine 5.5 gtetrabutylammonium hydroxide 1 g tetramethylammonium hydroxide 4.5 g H₂O3 g monoethanolamine 6-b 87 g DMSO NC NC C C 5 g 1-formylpiperidine 5.5g tetrabutylammonium hydroxide 4.5 g H₂O 3 g monoethanolamine 6-c 81 gDMSO C C C C 7 g tetrabutylphosphonium hydroxide 9 g H₂O 3 gmonoethanolamine 6-d 80.5 g DMSO NC C C C 0.5 g 1-formylpiperidine 7 gtetrabutylphosphonium hydroxide 9 g H₂O 3 g monoethanolamine 6-e 81 gDMSO C C C C 5 g 1-formylpiperidine 7 g tetrabutylphosphonium hydroxide9 g H₂O 3 g monoethanolamine C = clean and NC = not clean

Example 7 Minimizing the Change in the Low-κ Permittivity Value(AK) of aSubstrate

Blanket wafers of pristine Black Diamond II (BDII) were sectioned intoabout 1″×1″ samples. The samples were first put into the oven at 250° C.for 30 minutes to ensure that, prior to immersion in stripper solution,they obtained the low permittivity value (κ_(a)) that they had atdeposition. Results were recorded. The samples were then immersed in theformulation described in Example 5(c) for 60 seconds at 65° C., removed,rinsed with water and isopropyl alcohol, and dried. Permittivitymeasurements were made and the results recorded to provide a lowpermittivity value κ_(b). The dried samples were then placed in an ovenmaintained at 250° C. for 30 minutes. Permittivity measurements weremade and the results recorded (κ_(c)). [All permittivity values weremeasured on a Mercury Probe, model 802B from Materials DevelopmentCorporation, Chatsworth, Calif., www.mdc4ov.com and the results wererecorded.] A typical set of values obtained from this procedure includeκ_(a)=2.40; κ_(b)=2,87; and κ_(c)=2.49. The change in the lowpermittivity value (Δκ) obtained by removing volatiles is therefore2.49-2.40 or 0.09. Had the volatiles not been removed, the change in lowpermittivity value (Δκ) would have been 2.87-2.40 or 0.47. Maintaining aΔκ of ≦0.1 is necessary for successful implementation in a semiconductormanufacturing process using low-κBDII.

While applicant's invention has been described in detail above withreference to specific embodiments, it will be understood thatmodifications and alterations in embodiments disclosed may be made bythose practiced in the art without departing from the spirit and scopeof the invention. All such modifications and alterations are intended tobe covered. In addition, all publications cited herein are indicative ofthe level of skill in the art and are hereby incorporated by referencein their entirety as if each had been individually incorporated byreference and fully set forth.

1. A stripper solution for removing a resist from a substrate comprisinga polar aprotic solvent, water, an amine, and a quaternary hydroxide,wherein the quaternary hydroxide has the formula:

where Z is P and R¹, R², R³, and R⁴ are alkyl groups, benzyl, arylgroups, or a combination thereof having collectively at least 5 carbons.2. The stripper solution of claim 1, wherein the stripper solutionadditionally contains glycerine and the polar aprotic solvent isselected from the group consisting of dimethyl sulfoxide and1-formylpiperidine.
 3. The stripper solution of claim 1, wherein theaprotic solvent comprises from about 40% to about 90% of thecomposition; water comprises from about 2% to about 15% of thecomposition; the quaternary hydroxide comprises from about 1% to about10% of the composition; and the amine comprises from about 2% to about60% of the composition.
 4. The stripper solution of claim 3, wherein theaprotic solvent is dimethyl sulfoxide.
 5. The stripper solution of claim1, wherein Z is P.
 6. The stripper solution of claim 3, wherein saidamine is an alkanolamine having at least two carbon atoms, at least oneamino substituent and at least one hydroxyl substituent, the amino andhydroxyl substituents attached to different carbon atoms.
 7. Thestripper solution of claim 3, wherein the quaternary hydroxide comprisestetrabutyl phosphonium hydroxide, tetraphenyl phosphonium hydroxide,methyl triphenyl phosphonium hydroxide, ethyl triphenyl phosphoniumhydroxide, propyl triphenyl phosphonium hydroxide, butyl triphenylphosphonium hydroxide, benzyl triphenyl phosphonium hydroxide, allyltriphenyl phosphonium hydroxide, dodecyl triphenyl phosphoniumhydroxide, tetradecyl triphenyl phosphonium hydroxide, hexadecyltriphenyl phosphonium hydroxide, hexadecyl tributyl phosphoniumhydroxide, carbethoxyethyl triphenyl phosphonium hydroxide,carbmethoxyethyl triphenyl phosphonium hydroxide, carbethoxymethyltriphenyl phosphonium hydroxide, or carbmethoxymethyl triphenylphosphonium hydroxide.
 8. The stripper solution of claim 7, wherein thequaternary hydroxide comprises tetrabutylphosphonium hydroxide.
 9. Thestripper solution of claim 1, wherein the stripper solution containssubstantially no tetramethylammonium hydroxide.
 10. A method forremoving a resist from a substrate comprising: (a) providing a substratehaving a resist thereon; (b) contacting the substrate with a strippersolution for a time sufficient to remove the resist; (c) removing thesubstrate from the stripping solution; and (d) rinsing the strippersolution from the substrate with a solvent, wherein the step ofcontacting the substrate with a stripper solution involves contactingthe substrate with a stripper solution including a polar aproticsolvent, water, an amine, and a quaternary hydroxide having the formula:

where Z is P and R¹, R², R³, and R⁴ are alkyl groups, benzyl, arylgroups, or a combination thereof having collectively at least 5 carbons.11. The method of claim 10, wherein contacting the substrate with astripper solution includes contacting the substrate with a strippersolution including a polar aprotic solvent comprising from about 40% toabout 90% of the composition; water comprising from about 2% to about10% of the composition; the quaternary hydroxide comprising from about1% to about 10% of the composition; and the amine comprising from about2% to about 65% of the composition
 12. The method of claim 11, whereincontacting the substrate with a stripper solution includes contactingthe substrate with a stripper solution, wherein the polar aproticsolvent is dimethyl sulfoxide.
 13. The method of claim 11, whereincontacting the substrate with a stripper solution includes contactingthe substrate with a stripper solution, wherein the polar aproticsolvent is 1-formylpiperidine.
 14. The method of claim 10, whereincontacting the substrate with a stripper solution includes contactingthe substrate with a stripper solution including an amine whichcomprises an alkanolamine having at least two carbon atoms, at least oneamino substituent and at least one hydroxyl substituent, the amino andhydroxyl substituents attached to different carbon atoms.
 15. The methodof claim 10, wherein contacting the substrate with a stripper solutionincludes contacting the substrate with a stripper solution having aquaternary hydroxide selected from the group consisting oftetrabutylammonium hydroxide, tetraphenyl phosphonium hydroxide, methyltriphenyl phosphonium hydroxide, ethyl triphenyl phosphonium hydroxide,propyl triphenyl phosphonium hydroxide, butyl triphenyl phosphoniumhydroxide, benzyl triphenyl phosphonium hydroxide, allyl triphenylphosphonium hydroxide, dodecyl triphenyl phosphonium hydroxide,tetradecyl triphenyl phosphonium hydroxide, hexadecyl triphenylphosphonium hydroxide, hexadecyl tributyl phosphonium hydroxide,carbethoxyethyl triphenyl phosphonium hydroxide, carbmethoxyethyltriphenyl phosphonium hydroxide, carbethoxymethyl triphenyl phosphoniumhydroxide, or carbmethoxymethyl triphenyl phosphonium hydroxide.
 16. Themethod of claim 10, wherein contacting the substrate with a strippersolution includes immersing the substrate in the stripping solution withagitation at a temperature of at least about 40° C.
 17. The method ofclaim 10, wherein contacting the substrate with a stripper solutionincludes spraying the stripper solution onto the substrate, wherein thestripper solution is at a temperature of at least about 40° C.,
 18. Themethod of claim 10, wherein contacting the substrate with a strippersolution includes contacting the substrate with a stripper solutionhaving substantially no tetramethylammonium hydroxide.
 19. The method ofclaim 10, wherein providing a substrate having a resist thereon,involves providing a substrate having a resist which is a bilayer resisthaving two polymer layers.
 20. The method of claim 10, wherein providinga substrate having a resist thereon, involves providing a substratehaving a resist which is a bilayer resist having one inorganic layer andone polymer layer.
 21. The method of claim 10, further comprising thestep of removing adsorbed volatiles from the substrate to obtain aprocessed substrate, wherein providing a substrate includes providing asubstrate having a low-κ permittivity value identified as κ_(a) andobtaining a processed substrate includes obtaining a processed substratehaving a low-κ permittivity value identified as κc_(c), wherein, Δ κ isdefined as the difference between κ_(c) and κ_(a), and wherein Δκ≦0.122. An electronic device prepared according to a process comprising: (a)providing a substrate having a resist thereon; (b) contacting thesubstrate with a stripper solution for a time sufficient to remove adesired amount of resist; (c) removing the substrate from the strippingsolution; and (d) rinsing the stripper solution from the substrate witha solvent, wherein contacting the substrate with a stripper solutioninvolves contacting the substrate with a stripper solution including apolar aprotic solvent, water, an amine, and a quaternary hydroxidehaving the formula:

where Z is N and R¹, R², R³, and R⁴ are alkyl groups, benzyl, arylgroups, or a combination thereof having collectively at least 5 carbons.23. A method for preparing a BEOL stripper solution comprising the actsof: (a) providing a container; (b) providing components of the strippersolution formulation; and (c) adding said components of said strippersolution to said container to provide contents, wherein said providingcomponents involves providing a polar aprotic organic solvent, water, anamine, and a quaternary hydroxide, the quaternary hydroxide having theformula:

where Z is P and R¹, R², R³, and R⁴ are alkyl groups, benzyl, arylgroups, or a combination thereof having collectively at least 5 carbons.